The present invention relates to speaker assemblies for personal use such as in mobile terminals and, more particularly, to tuned micro-speaker assemblies.
Manufacturers and designers of personal electronic devices, such as cellular radio telephones, frequently seek to reduce the overall dimensions of such devices while maintaining attractive style characteristics for the devices. One consequence of the reduced size for such devices that include a speaker is that less space may be available for the speaker. Furthermore, a variety of audio signal generation capabilities may be desired in such personal electronic devices including buzzers, voice signal generation and/or music or other higher frequency band signal reproduction and playback.
As the space available for the hardware supporting the audio signal generation capabilities decreases in the personal electronic devices, it may become more difficult to support multiple sound emitting output devices and the space available for each such device may become smaller. Furthermore, increased functionality in such personal electronic devices may require more of the reduced available space to be utilized for other functionality of the device. The reduction in the size of the audio output devices may also increase the difficulty of providing a desirable loudness level for signals, such as buzzer alert signals. In addition, to the extent features of the audio output device(s) are presented externally on the personal electronic device, the impact of those features on the appearance of the product and the flexibility to place such visible features at different locations on the device may become important.
A micro-speaker is typically positioned in a personal electronic device with its front face or side ported (acoustically connected) to outside of the device while the back side is ported to a back tuning volume. As a result, positioning of the micro-speaker in the device may be limited. For example, placement on a reverse side of a printed circuit board of the personal electronic device may be precluded. It may also be difficult to seal the back tuning volume, which may result in weaker bass output and higher distortion. In addition, user dissatisfaction may result if higher volume signals port high acoustic levels too close to a user's ear.
For audio performance, it is known to use a speaker having relatively uniform frequency characteristics in the 300 hertz (Hz) to 3400 Hz voice frequency band. Where music or other complex signals are provided by the device, a speaker with a frequency range providing a bandwidth up to at least about 8000 Hz may be used. In addition, louder alert signals may be provided in various personal electronic devices.